Nicholas was by all accounts a happy 10-month-old boy living in Sudbury, Ont.

"He was the light of our lives," recalls his mom Lianne Thibeault.

"Saturday morning was dance time. Every Saturday morning I would pick him and we would dance to Sleepwalk," Nicholas' grandfather Maurice Gagnon tells The Current's Anna Maria Tremonti.

The light of their lives went out on Nov. 30, 1995, when Nicholas accidentally banged his head on a sewing machine.

"He had let out a really loud sharp cry as he went down ... I was waiting for that big gasp of air so he can continue with his cry and it never came," Lianne recounts.

"So when I looked at him I could tell that he wasn't breathing."

Later that day Nicholas was pronounced dead in hospital.

Almost 18 months after Nicholas had died, police told Lianne Thibeault that she was a suspect for her son's death. (Courtesy of Lianne Thibeault)

A local pathologist did the autopsy, categorizing the cause of death as Sudden Infant Death Syndrome. But months later, a supervisor found an error in the post-mortem report: the cause of death should have been classified as a Sudden Unexplained Death. That relatively minor error triggered a review, which fell to Charles Smith, the now-disgraced and incompetent pediatric pathologist.

At that time, he was head of the Ontario Pediatric Forensic Pathology Unit and the most highly regarded specialist in his field. Smith dismissed all of the original pathologist's findings. He argued that Nicholas couldn't have died from a simple bump on the head the way his mother described, ruling instead that blunt force trauma was the cause of death.

Lianne Thibeault had gone from being a grieving parent to a murder suspect.

"[The police] informed me they didn't believe my story and that a doctor in Toronto had reviewed Nicholas autopsy results and believed I was responsible for his death," Lianne tells Tremonti after she was taken into police custody.

Smith wanted to exhume Nicholas' body and do a second autopsy. When Lianne arrived at the cemetery, she says she was shocked by what she saw.

Charles Smith with his 11-year-old son at the exhumation of Nicholas, Lianne Thibeault's son. (Courtesy of Maurice Gagnon)

"I could see a group standing beside my son's grave and they were still in the process of pulling the dirt out of the ground," says Lianne.

"I could see a little boy playing in the dirt. I was furious."

That little boy was Charles Smith's son. Smith said he brought his son to Sudbury to help keep him awake during the long drive from Toronto. The chief coroner later admitted the child should not have been present at the exhumation.

The Crown did not proceed with charges against Lianne, but that was not the end of Lianne's ordeal. She was pregnant, and Children's Aid announced it would be apprehending her unborn daughter at birth because of the police investigation into Nicholas' murder.

"During my first trimester of pregnancy, I was being accused of murder and did not know whether or not I would be going to jail."

"And in my third trimester, I was being told my baby was going to be taken away at birth."

Children's Aid seized the child at birth. She was placed with her grandparents, who acted as de facto foster parents. Lianne was allowed limited access and required strict supervision.

A public inquiry was called after an Ontario coroner's inquiry questioned Dr. Charles Smith's conclusions in 20 of 45 child autopsies. (Adrian Wyld/Canadian Press)

Maurice Gagnon spent more than $100,000 over the next six months hiring a top Sudbury lawyer and searching for medical experts and pathologists to challenge Smith's opinions. He found several who felt Nicholas' death had been a tragic accident.

Faced with competing opinions, the provincial chief coroner's office hired its own independent pathologist to review the case again. Dr. Mary Case's report finally put the matter to rest: She found no evidence of foul play; she said Nicholas could have died from bumping his head. Lianne's explanation of what happened was entirely plausible.

Children's Aid dropped its application, and Lianne's daughter was returned to her care.

Nicholas' case is only one of 20 identified in a 2008 judicial inquiry where findings by Charles Smith were mistaken and led to several wrongful convictions.

New book chronicles the many tragedies caused by disgraced pathologist

Smith's work and testimony ruined many lives and The Current's producer John Chipman details the wreckage wrought by Charles Smith in his new book, Death in the Family.

He tells Tremonti that he spent four years interviewing dozens of people, digging through thousands of documents and piecing together what went wrong.

"The key thing for Charles Smith is he did not know how to be objective. He thought he had all the answers," says Chipman.

He says the problem was that Smith, who was never charged for his irresponsible conduct, was ill-equipped to hold such an important position.

Chipman goes on to say that Smith had no certification or specialized training in forensic pathology, but "his supervisors didn't see that as a problem."

"He became so narrow-minded in terms of his opinions. As new information came in and other people looked at it, he would not give it up," Chipman tells Tremonti.

Charles Smith was a key figure in investigating child deaths in Ontario throughout the 1990s as the head of the Ontario Pediatric Forensic Pathology Unit at the Hospital for Sick Children in Toronto.

"[Charles Smith] is a person who we as a culture and society normally lionize. He saw himself as the last line of defence for defenceless children."

Chipman says he does not know where Charles Smith is today and multiple attempts to reach him were not successful.